<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../vue.js"></script>
</head>

<body>
  <div id="app">
    <button @click = "isHot = !isHot">切换</button>
    {{isHot}}
  </div>
  <script>
    Vue.config.productionTip = false;
    
    const vm = new Vue({
      el: "#app",
      data() {
        return {
          isHot: true
        }
      },
      //之前写法
      // watch:{
      //   isHot:{
      //     handler(){
      //       console.log("isHot改变了");
      //     }
      //   }
      // }
      //不用立即监听和深度监听的时候可以简写
      watch:{
        isHot(){
          console.log("isHot执行了");
        }
      }
    })
  </script>
</body>

</html>